Wettability is a property to measure the interaction between a fluid and a solid surface in the presence of other immiscible fluids. Wettability can be defined by the contact angle of the fluid with the solid surface. Regarding oil production, the wettability of a rock formation can affect the oil extraction process. Rock formations can be described as being water-wet, intermediate wet, or oil-wet, which translate to contact angle ranges of approximately 0° to 75°, 75° to 105°, and 105° to 180°, respectively. A shift from oil-wetness to water-wetness of a rock formation can generally increase oil production from the formation.
Contact angle measurement can include observing the behavior of a small amount of fluid, such as a droplet or gas bubble, on a solid surface. Contact angle measurements can be taken on a stationary droplet (static contact angle) or a moving droplet (dynamic contact angle). Porous media, such as rock, is typically more complex and can have several configurations due to the varied geometry and mineralogy of pore space. The wettability of rock formations can therefore be heterogeneous, and heterogeneous wettability can further affect hydrocarbon recovery from rock formations in which the hydrocarbons are trapped.